Method for manufacturing master substrate used for manufacturing grooved molding substrate, method for manufacturing stamper for manufacturing grooved molding substrate, method for manufacturing grooved molding substrate, grooved molding substrate, memory medium, memory device, and computer

ABSTRACT

A substrate having a photoresist coated thereon is exposed to exposure light along a line through a lens  1 . The exposure position is moved from the initial position O 1  to a position O 2  that is separated from the initial position by a distance corresponding to the sum of a groove width Gw and a land width Lw. The exposure is carried out along a line parallel to the initial exposure line. By repeating this, exposed areas having a width Lw and a separation Gw are formed on the photoresist. The photoresist is developed to remove the exposed areas of the photoresist. A resin or the like is pressed on it to form a replica. From the replica, a stamper is manufactured using an electroforming method. Finally, a grooved molding substrate is manufactured from a glass or resin using the stamper. Although the land width Lw is defined by the effective spot diameter φ of the optical system, the groove width Gw can be less than this value.

[0001] This application is a continuation of PCT InternationalApplication No. PCT/JP99/03345, filed on Jun. 23, 1999, which in turnclaims the benefit of Japanese Application No. 11-153278, filed in Japanon Jun. 1, 1999, both of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a grooved molding substrate (asubstrate formed by a stamper), which has narrow grooves (on which pitsare formed) and is used for optical disks, magneto-optical disks, harddisks (magnetic disks), and the like, and a method for manufacturing thesame. Moreover, the present invention relates to a method formanufacturing a master substrate used for manufacturing the aforesaidgrooved molding substrate and the stamper. Furthermore, the presentinvention relates to a recording medium using the grooved moldingsubstrate, a memory device using the recording medium, and a computerusing the memory device. Since the grooved molding substrate accordingto the present invention can be formed to have narrow grooves having thewidth of 0.23 μm or less, the recording density can be enhanced byapplying the present invention to optical disks, magneto-optical disks,hard disks, and the like.

[0004] 2. Discussion of the Related Art

[0005] Data recording media, such as optical disks, hard disks, and thelike, are capable of recording large quantities of information. Suchdata recording media are commonly referred to as CD's (compact disks),LD's (laser disks), DVD's (digital video disks, or digital versatiledisks), etc. These data recording media may contain music, movies,software, etc. Such media also are used as storage devices in computers.Demand for such recording media is expanding greatly. Indeed, it isanticipated that optical disk and hard disk usage will continue toexpand because these are the major recording media of the multimediaage.

[0006] Optical disks are classified according to the existence orabsence of a recording layer, and are further classified according tothe type of recording layer. Optical disk types include:

[0007] (1) The read-only type (CD, LD, CD-ROM, photo-CD, DVD-ROM,read-only type MD, etc.);

[0008] (2) The write-once type (CD-R, DVD-R, DVD-WO, etc.); and

[0009] (3) The rewritable type capable of erasure followed by writingany number of times (magneto-optical disk, phase-change type disk, MD,CD-E, DVD-RAM, DVD-RW, etc.).

[0010] Moreover, the high density HD-DVD has also been proposed as amedium of the future.

[0011] Processes for manufacturing these optical disks begin with themolding of a raw material resin into a resin substrate. A raw materialresin, for example, polycarbonate, acrylate resin, polystyrene, etc., isheated, melted or partially melted, and then is pressed using a stamper,thereby molding (manufacturing) a resin substrate. Typically, themolding method used is a pressure molding or injection molding method.The stamper forms fine concavities and protuberances which representinformation copied upon the substrate surface. Other than resin molding,there is no such method for manufacturing large quantities of substratesthat have minute concavities and protuberances in a short time period.

[0012] Types of pits and protuberances include:

[0013] (1) Pits that indicate a unit of information; and

[0014] (2) Guide grooves that are provided for tracking by the pickuphead.

[0015] Generally, the manufacture of data recording media involvescircular substrates provided with pits and grooves on the substratesurface in the pattern of concentric circular rings or in a spiralpattern. The region between grooves along the radial direction is calleda “land.” Recording upon the lands occurs in the land recording method,or alternatively, recording occurs within the groove in the grooverecording method.

[0016] In order to improve the recording density, the land/grooverecording method was developed to record upon both the grooves and thelands. In this case, both grooves and lands are tracks, and the groovewidth Gw and the land width Lw are nearly equal. However, there arereasons for sometimes deliberately widening one or the other. Incidentlight enters the backside surface (flat smooth surface) of thesubstrate. In this case, the portion of the concavities andprotuberances that is far from the backside surface is called “a land,”and the portion of the concavities and protuberances that is close tothe backside surface is called “a groove.”

[0017] As the recording density increased, to meet the increased needfor a larger storage capacity, the groove width, land width, and the pitwidth have decreased and their depth has increased. For example, thewidth has decreased from <1 μm to <0.3 μm and the depth has increasedfrom >40 nm to >250 nm. As the width decreases and the depth increases(i.e., as the density becomes higher), molding of the resin substratebecomes increasingly difficult, and the yield of good products declines.

[0018] When manufacturing a hard disk, a magnetic recording layer istypically formed or deposited on an aluminum or glass substrate withrecording carried out by a magnetic head. A reflection layer, arecording layer and a protection layer may then be formed on the resinsubstrate to produce the desired final product.

[0019] As the recording density increases, the recording layer becomesextremely flat and smooth. When the magnetic head becomes relativelystill, the recording head and the recording layer adhere to one anotherand cannot separate. In order to avoid this phenomenon, a garage region(CSS region=contact stop and start) is provided. The surface of thisgarage region is deliberately finished with a rough texture using alaser so that surface adherence is prevented. Head tracking also becomesdifficult as recording density increases. Therefore, it is proposed thata magnetic hard disk should be provided with grooves like an opticaldisk. Due to a demand for such roughness and grooves, resin substratesare proposed as a means to increase manufacturing productivity.Increased productivity results due to the formation of roughness andgrooves in the substrate molding. In this case, material of thesubstrate is resin or low-melting glass.

[0020] Previously, molding tools were manufactured by the processdescribed in Hunyar, U.S. Pat. No. 4,211,617, which corresponds toJapanese Patent publication Sho 59-16332, the disclosures of which arehereby incorporated by reference in their entirety. This related art(Hunyar) is explained with reference to FIGS. 9A to 11.

[0021] Generally, molding tools are manufactured using a glass substrate3 that is polished with the precision of an optical surface. After thesubstrate 3 is cleaned, it is coated with a primer, for example, asilane-coupling agent. A photoresist 2 is then applied by spin coatingand subjected to a pre-bake process. Positive-type photoresist 2, i.e.,the type in which the region exposed to light is removed by development,is often used. This is because the surface roughness can be made smallerby the positive-type photoresist to have lower noise, which isadvantageous. The following descriptions assume use of a positive-typephotoresist.

[0022] Next, a laser beam recorder or a laser cutting machine is used toexpose the photoresist 2 with a pattern of pits and/or grooves. Thewidth of pits and grooves is generally determined by the laser spotdiameter. In this case, in order to make the laser spot diameter asnarrow as possible (i.e., to obtain a higher density), the laser beam isconverged to the diffraction limit by a lens 1. On the other hand, thedepth of the pits and grooves is generally determined by the thicknessof the photoresist 2.

[0023] The case where a plurality of grooves exit in the pattern ofconcentric circular rings is explained in more detail. First, thephotoresist 2 is illuminated by a predetermined exposure light along thefirst line O₁ via lens 1 (FIG. 9A). The illumination is continuous whenforming grooves, and is intermittent when forming pits. The illuminatedarea (exposed area) becomes the first groove of the molding substrateafterward. In this method, the spot diameter of the exposure lightdirectly defines the line width of the “exposed area” (hereinafter, the“exposed area” may also be referred to as “exposure area”). In thiscase, the minimum spot diameter is defined by the diffraction limit ofthe exposure light, and it depends on the wavelength λ of the exposurelight. Because the light intensity distribution in the light beamexhibits the Gaussian distribution, the intensity is the strongest atthe center and becomes weaker at the periphery. Therefore, the effectivespot diameter (diameter of the removed area of the exposed photoresistby development) becomes smaller than the value determined by thediffraction limit because of the sensitivity of the photoresist and thedeveloping condition. When an exposure method called a “narrow pencilwriting,” which uses only the center of the light beam by weakening theoutput of the light source, is used, the effective diameter can be madeeven smaller. In the conventional method, the effective spot diameter φdetermines the groove width of the resist pattern, and accordingly,determines the groove width Gw of the molding substrate. In FIGS. 9A-9B,φ denotes the effective spot diameter.

[0024] At present, an argon laser light having the wavelength λ=351 nmis used for the exposure light. In this case, the minimum effective spotdiameter φ is 0.23 μm. Accordingly, the minimum groove width Gw of themolding substrate that can be obtained is about 0.23 μm which is almostequal to φ (i.e., φ=groove width Gw).

[0025] When the groove width Gw needs to be large, the spot diameter isnot made small to the diffraction limit, or exposure light in theout-of-focus condition is used. When the desired line width cannot beobtained by one exposure, another exposure similar to the first exposurecan be performed repeatedly with the illuminating position moved by anappropriate distance. At any rate, the illuminating position is thenmoved from the first line O₁ to the second line O₂ separated by thedistance corresponding to the sum of the groove width Gw and the landwidth Lw (which is parallel to the first line) (FIG. 9B).

[0026] After moving the exposure light to the position of the secondline O₂, the photoresist is illuminated (exposed). Generally, thisprocess is repeated plural times successively regarding the second lineO₂ as the first line O₁. This way, a plurality of the exposure areas 2 eof concentric circular rings is obtained (FIG. 9C).

[0027] A resist pattern having grooves and pits on the substrate surfaceis obtained by developing the exposed photoresist. Following thedevelopment, the resist pattern may optionally undergo a 20 to 60-minutepost-bake at 80-120° C. When such a post-bake is used, the resistpattern is then cooled down to a room temperature. This is shown in FIG.10A.

[0028] The resist pattern in combination with the substrate 3 shown inFIG. 10A is called the master substrate or master 4. The mastersubstrate 4 is equivalent to the replica 46 in FIG. 4 of Hunyar U.S.Pat. No. 4,211,617.

[0029] The master substrate 4 undergoes a metallization treatment toform a conductive layer on the surface. Generally such a treatment iscarried out by sputtering (dry-type method), or by non-electrolyticplating (wet-type method). Following the metallization, a thick platinglayer, such as nickel (Ni), is formed on the master substrate 4 by anelectroforming method. The double layer structure that is made of theconductive layer and the Ni plating layer is referred to as the “fatherstamper” or just the “father” or “stamper.” This is shown in FIG. 10B. Afree stamper 5 is obtained when the stamper 5 is peeled off from themaster substrate 4. This is indicated in FIG. 10C. The stamper 5 isequivalent to mother member 52 in FIG. 6 of Hunyar U.S. Pat. No.4,211,617.

[0030] Care must be taken during peeling since the stamper 5 isgenerally thin, approximately 200-300 μm in thickness. After peeling,the stamper 5 undergoes a solvent treatment, such as acetone treatmentor the like, to remove the resist since a portion of the resist mayremain on the stamper 5. The resist must be removed since theconcavities and protuberances on the surface of the stamper would nototherwise be destroyed. Only a single stamper 5 is obtained from asingle master substrate 4 since the resist pattern 2 is damaged duringthe peeling. The resulting stamper 5 has an extremely precise pattern ofconcavities-protuberances. Because the stamper 5 after peeling has arather inaccurate outer dimension, a central hole is bored in the centerof the stamper 5, and the unused portion of the outside perimeter is cutoff. Before further processing, the concavity-protuberance surface(signal surface) is shielded with a protective coat. Thus, an annularshaped stamper 5 is obtained.

[0031] Then, a molding substrate is formed by using the stamper 5. Asoft resin (or liquid resin) 6 is pressed against the stamper 5. This isshown in FIG. 10D. Accordingly, the concavities-protuberances of thestamper 5 are embossed on the resin. After cooling it down, the hardenedor cured resin 6 is peeled off from the stamper 5 to form a moldingsubstrate 6 shown in FIG. 11. The molding substrate 6 has theconcavities-protuberances formed by grooves having the width Gw and thelands having the width Lw, which are disposed alternately. In order tomanufacture the molding substrate, pressure molding or injection moldingcan be used. Generally, injection molding is used because of its highproductivity.

[0032] As explained above, the width Gw of grooves (pits and dints, etc,are also generally referred to as “grooves”) is determined by thewavelength λ and the effective spot diameter φ. Therefore, the moldingsubstrate having the groove width Gw narrower than φ cannot be obtained.Since argon laser (λ=351 nm) is used presently, the minimum groove widthGw that can be formed is about 0.23 μm (230 nm). If the wavelength i canbe made smaller, it may be possible to reduce the groove width Gw.However, a proper light source having a shorter wavelength than that ofargon laser has not been available to date because there exists noappropriate laser having a shorter wavelength with continuousoscillation, or photoresist that has sensitivity to such a shortwavelength λ (ultraviolet light) and that makes it possible to etchgroove walls vertically. Accordingly, the groove width Gw has theshortest value of about 0.23 μm thus far. However, as the demand forhigher recording densities increases, development of technology capableof forming a finer groove width Gw has been strongly desired.

SUMMARY OF THE INVENTION

[0033] Accordingly, the present invention is directed to a method formanufacturing grooved molding substrate, a grooved molding substrate, amethod for manufacturing a master substrate for use in manufacturing thegrooved molding substrate, and a method for manufacturing a stamper foruse in manufacturing the grooved molding substrate that substantiallyobviate the problems due to limitations and disadvantages of the relatedart.

[0034] An object of the present invention is to provide a moldingsubstrate having a groove width Gw finer than the finest groove width(=φ) that is available in the conventional art, and a method for formingthe same.

[0035] Another object of the present invention is to provide a methodfor manufacturing a master substrate and a stamper for fabricating themolding substrate with the aforementioned grooves.

[0036] A further object of the present invention is to provide animproved memory medium using the aforementioned molding substrate withthe grooves, an improved memory device using the recording medium, and acomputer using such an improved memory device.

[0037] Additional features and advantages of the invention will be setforth in the description that follows, and in part will be apparent fromthe description, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0038] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly described, themethod for manufacturing a master substrate for producing a groovedmolding substrate includes a preparing step that prepares a substrate onwhich a photoresist is coated; an exposing step that exposes thephotoresist to light with a predetermined pattern such that the exposedpart corresponds to a land of the grooved molding substrate to beproduced; and a developing step that obtains the master substrate bydeveloping the photoresist.

[0039] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0041] In the drawings:

[0042] FIGS. 1A-1C, 2A-2C, 3, and 4A-4C illustrate a method for forminga grooved molding substrate according to a first preferred embodiment ofthe present invention;

[0043] FIGS. 5A-5C, 6A-6D, and 7 illustrate a method for forming agrooved molding substrate according to a second preferred embodiment ofthe present invention;

[0044]FIGS. 8A and 8B show master substrates according to preferredembodiments of the present invention;

[0045] FIGS. 9A-9C, 10A-10D, and 11 illustrate a method for forming agrooved molding substrate according to the conventional art;

[0046]FIG. 12 is a schematic cross-sectional view of a hard diskaccording to the present invention;

[0047]FIG. 13 is a block diagram of a hard disk driver according to thepresent invention; and

[0048]FIG. 14 is a block diagram of a computer according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Before describing the preferred embodiments of the presentinvention, work by the inventors, which lead to the present invention,is explained. As a result of diligent studies, the inventors discoveredthe following:

[0050] (1) When the land on a molding substrate is formed by the exposedarea of a resist, and the groove width is determined by the separationbetween the first line and the second line, the groove width can be madesmaller than the effective spot diameter φ.

[0051] (2) When a positive type photoresist is used, instead ofmanufacturing a stamper directly from a master substrate, after areplica (which has the surface profile that is reverse of the mastersubstrate) is formed from the master substrate, a usable stamper can bemanufactured from the replica such that the stamper has a surfaceprofile that is same (that is, not reversed) concavities-protuberancesas the master substrate.

[0052] Owing to these discoveries, the prevent invention provides, in afirst aspect, a method for manufacturing a master substrate forproducing a grooved molding substrate, including a preparing step thatprepares a substrate on which a photoresist is coated; an exposing stepthat exposes the photoresist to light with a predetermined pattern suchthat the exposed part becomes a land of the grooved molding substrate,and a developing step that obtains the master substrate by developingthe photoresist.

[0053] When the photoresist is of positive type, a replica is formedusing the master substrate, and a stamper is manufactured using thereplica. In contrast, when the photoresist is of negative type, astamper is manufactured directly from the master substrate. A moldingsubstrate can be manufactured using either stamper. Therefore, in themaster substrate according to the first aspect of the present invention,a photoresist area (exposed area) where a pattern is exposed becomes anarea corresponding to the lands (not groove) in the molding substrate,which is final product. Accordingly, the land width Lw is determined bythe wavelength of the exposure light. The groove width Gw is determinedby the separation between the adjacent exposed areas. In the presentinvention, the master substrate is manufactured by suitably arrangingthe separation between the adjacent exposed areas. By using such amaster substrate, a narrow-grooved molding substrate that has beenimpossible to make can successfully be manufactured. (In the presentinvention, the remaining photoresist after development forms theprotuberant portion, and the area where the photoresist was removedforms the concave portion in the master substrate. When the photoresistis removed all the way in the thickness direction, the groove depthformed in the grooved molding substrate corresponds to the thickness ofthe photoresist.)

[0054] In a second aspect, the present invention provides a method formanufacturing a master substrate for producing a grooved moldingsubstrate, including a preparing step that prepares a substrate on whicha photoresist is coated, an exposing step that exposes the photoresistto light with a predetermined pattern such that the exposed part becomesa land of the grooved molding substrate, a development step that createsa resist pattern by developing the photoresist, an etching step thatetches a part of the substrate not covered by the photoresist, and aremoval step that obtains the master substrate by removing thephotoresist.

[0055] This aspect of the present invention also has similar effects tothe first aspect. In addition, a master substrate that can be usedrepeatedly is obtained by suitably choosing the material of thesubstrate. Moreover, since the groove depth can be controlled by theetching depth, a deep groove that has been impossible to manufacture canbe manufactured, and a groove having a steep sidewall and a smoothbottom surface can also be manufactured.

[0056] In a third aspect, the present invention provides a method formanufacturing a master substrate for producing a grooved moldingsubstrate, including a first step that prepares a substrate on which aphotoresist is coated, a second step that forms a part corresponding toa first land of the grooved molding substrate by illuminating andexposing the photoresist along a first line with exposing light, a thirdstep that moves the illuminating position from the first line to asecond line that is separated from the first line by a distancecorresponding to the sum of a groove width Gw and a land width Lw of thegrooved molding substrate, a fourth step that forms a part correspondingto a second land of the grooved molding substrate by illuminating andexposing the photoresist along the second line with the exposing light,and a fifth step that obtains the master substrate by developing thephotoresist. In the case of forming a spiral pattern on a groovedmolding substrate, the second through fourth steps above may be replacedwith a step that forms a part corresponding to a spiral shaped land of agrooved molding substrate by illuminating and exposing along a spiralline having an interval corresponding to a distance corresponding to thesum of a groove width Gw and a land width Lw of the grooved moldingsubstrate.

[0057] Using the master substrate manufactured by the third aspect ofthe present invention above, a narrow-grooved molding substrate that hasbeen impossible to make can be manufactured for the reasons similar tothose in the first aspect of the present invention. (In the presentinvention, the remaining photoresist after development forms theprotuberant portion, and the area where the photoresist was removedforms the concave portion in the master substrate. When the photoresistis removed all the way in the thickness direction, the groove depthformed in the grooved molding substrate corresponds to the thickness ofthe photoresist.)

[0058] In the third aspect of the present invention above, the secondthrough fourth steps are used for manufacturing a grooved moldingsubstrate having the pattern of concentric circular rings. On the otherhand, when a grooved molding substrate having a spiral pattern is to bemanufactured, instead of the second through fourth steps, a step thatforms a part corresponding to a spiral shaped land of a grooved moldingsubstrate is performed by illuminating and exposing the photoresistalong a spiral line having an interval corresponding to a distancecorresponding to the sum of a groove width Gw and a land width Lw of thegrooved molding substrate. It is needless to say that the first andfifth steps are needed in either case.

[0059] In the third aspect of the present invention, adjacent exposureareas are separated by a distance corresponding to the sum of a groovewidth Gw and a land width Lw of the grooved molding substrate to bemanufactured (referred to as “exposure separation”). The land width Lwis determined by the exposure condition. The groove width is determinedby the exposure separation amount subtracted by the land width Lw. Thus,a desired groove width Gw can be obtained because the exposureseparation is set as described above. Since the groove width Gw is notdetermined by the exposure condition, the groove width can be made lessthan the effective spot diameter φ.

[0060] In a fourth aspect, the present invention provides a method formanufacturing a master substrate for producing a grooved moldingsubstrate, including a first step that prepares a substrate on which aphotoresist is coated, a second step that forms a part corresponding toa first land of the grooved molding substrate by illuminating andexposing the photoresist along a first line with exposing light, a thirdstep that moves the illuminating position from the first line to asecond line that is separated from the first line by a distancecorresponding to the sum of a groove width Gw and a land width Lw of thegrooved molding substrate, a fourth step that forms a part correspondingto a second land of the grooved molding substrate by illuminating andexposing the photoresist along the second line with the exposing light,a fifth step that obtains a resist pattern by developing thephotoresist, a sixth step that etches a part of the substrate notcovered by the photoresist, and a seventh step that obtains the mastersubstrate by removing the photoresist. In the case of forming a spiralpattern on the master substrate, the second through fourth steps may bereplaced with a step that forms a part corresponding to a spiral shapedland of a grooved molding substrate by illuminating and exposing thephotoresist along a spiral line having an interval corresponding to adistance corresponding to the sum of a groove width Gw and a land widthLw of the grooved molding substrate.

[0061] While the third aspect of the present invention usesconcavity-protuberance of the developed resist pattern in the mastersubstrate, the fourth aspect of the present invention uses the etchedportion as the concave portion, and the remaining portion as theprotuberant portion, as in the case of the second aspect of the presentinvention above. The groove depth of the grooved molding substrateformed by using the master substrate manufactured by the methodaccording to the fourth aspect of the present invention is determined bythe etching depth. This invention also has effects similar to those ofthe third aspect of the prevent invention. In addition, the groove depthcan be controlled by the etching depth, and a groove having a steepsidewall and a smooth bottom surface can also be manufactured.Accordingly, when the substrate is used for a medium, a grooved moldingsubstrate having low noise can be obtained. Moreover, this mastersubstrate can be used repeatedly.

[0062] After finishing the fourth step and before starting the fifthstep in the third and fourth aspects of the present invention above, acombination of the third and fourth steps may be carried out a pluralityof times by regarding the second line in the fourth step as the firstline in the subsequent third step.

[0063] By repeating the combination of the third and fourth steps aplurality of times, a master substrate for manufacturing a groovedmolding substrate having a plurality of grooves of concentric circularrings or parallel stripes, for example, can be manufactured.

[0064] In the third and fourth aspects of the present invention, thegroove width Gw may be set to about 0.1 μm or less. When such asubstrate is used for optical disks, magneto-optical disks, hard disks,and the like, the use of the groove width Gw of about 0.1 μm or less cangreatly increase the recording density relative to that of theconventional grooved molding substrate.

[0065] In the third and fourth aspects of the present invention, thegroove width Gw may be set to about 0.06 μm or less. When such asubstrate is used for optical disks, magneto-optical disks, hard disks,and the like, the use of the groove width Gw of about 0.06 μm or lesscan further increase the recording density relative to that of theconventional grooved molding substrate.

[0066] In the third and fourth aspects of the present invention, thegroove of the grooved molding substrate may be a hollow, a pit, ordiscontinuity. In such a case, since the groove of the grooved moldingsubstrate is a hollow, a pit or discontinuity, in a grooved moldingsubstrate formed by using the master substrate manufactured inaccordance with the present invention, the groove becomes a hollow, apit, or discontinuous. Accordingly, the arrangement of those canrepresent binary information.

[0067] In a fifth aspect, the present invention provides a method formanufacturing a stamper, including an additional step that, afterobtaining the master substrate manufactured by the method formanufacturing a master substrate for producing a grooved moldingsubstrate according to any one of the first to fourth aspects aboveusing a positive type photoresist as the photoresist, manufactures areplica from the master substrate, and a further additional step thatmanufactures the stamper from the replica by using an electroformingmethod.

[0068] In any one of the first through fourth aspects above, when apositive type photoresist is used, the exposed area becomes a concaveportion of the resist pattern. Therefore, if a stamper is directlymanufactured from the master substrate by using an electroformingmethod, the exposed area would correspond to the groove of the resultinggrooved molding substrate, which is similar to the conventional art.Accordingly, in order to reverse concavities-protuberances, a replica iscreated from the master substrate, and a stamper is manufactured fromthe replica by using an electroforming method or the like. Using theelectroforming method, an accurate stamper having a fine surfaceroughness can easily be manufactured.

[0069] In the fifth aspect above, the replica may be made of a metal orresin. When a metal is used for the replica, the replica is manufacturedfrom the master substrate by using an electroforming method. When aresin is used for the replica, the replica is manufactured by pressing aductile resin on the master substrate and curing it, and is duplicated.In either case, an accurate replica having a fine surface roughness canbe manufactured. It is preferable to use a resin because the replica canbe obtained more easily. Moreover, when concavities-protuberances isformed on the master substrate by etching, as in the case of the secondand fourth aspects above, the master substrate can be used repeatedly.

[0070] In a sixth aspect, the present invention provides a method formanufacturing a stamper for producing a grooved molding substrate,including an additional step that, after obtaining the master substratemanufactured by a method for manufacturing a master substrate forproducing a grooved molding substrate according to any one of the firstto fourth aspects above using a negative type photoresist as thephotoresist, manufactures the stamper from the master substrate by usingan electroforming method.

[0071] In any one of the first to fourth aspects above, if a negativetype photoresist is used, the exposed area corresponds to a protrudingportion of the resist pattern. Therefore, when a stamper is directlymanufactured from the master substrate by using an electroformingmethod, the exposed area becomes the land of the resulting groovedmolding substrate. Accordingly, a stamper is directly manufactured fromthe master substrate by using an electroforming method in contrast tothe fifth aspect of the present invention above. Using theelectroforming method, an accurate stamper having a small surfaceroughness can easily be manufactured.

[0072] In a seventh aspect, the present invention provides a method formanufacturing a stamper, including a preparing step that prepares asubstrate on which a photoresist is coated, an exposing step thatexposes the photoresist to light with a predetermined pattern, adeveloping step that creates a resist pattern by developing thephotoresist, an etching step that etches a part of the substrate notcovered by the photoresist, a removing step that obtains a mastersubstrate by removing the photoresist, a forming step that forms a resinreplica from the master substrate, and a manufacturing step thatmanufactures the stamper from the replica by using an electroformingmethod.

[0073] In the seventh aspect, since the pattern on the master substrateis constructed of the material of the substrate, the master substratecan be used many times when the substrate is made of a durable material.Moreover, since the etching depth can be controlled, the groove depth ofthe resultant grooved molding substrate can be controlled. Further, agrooved molding substrate having a small surface roughness can bemanufactured. Furthermore, by manufacturing a stamper from a resinreplica, the number of times the master substrate can be used increases.Since the electroforming method is used for manufacturing the stamperfrom the replica, an accurate stamper having a small surface roughnesscan be easily manufactured. A resin replica can be used repeatedly, andcan manufacture any number of stampers.

[0074] Stampers manufactured in accordance with the fifth and sixthaspects above are used to manufacture a grooved molding substrate byforming a glass or resin with the stampers.

[0075] Using the present invention, a grooved molding substrate whosegrooves correspond to unexposed areas of the master substrate can bemanufactured. Accordingly, a grooved molding substrate whose groovewidth is narrower than the effective spot diameter φ determined by thewavelength of the exposure light can be obtained.

[0076] In an eighth aspect, the present invention provides a groovedmolding substrate manufactured by an injection molding method using astamper, wherein the groove width Gw is about 0.1 μm or less. When sucha substrate having the groove width of about 0.1 μm or less is used foroptical disks, magneto-optical disks, hard disks, and the like, therecording density can be greatly increased relative to that of theconventional grooved molding substrate.

[0077] The groove width Gw may be set to about 0.06 μm or less. Whensuch a substrate having the groove width of about 0.06 μm or less isused for optical disks, magneto-optical disks, hard disks, and the like,the recording density can be further greatly increased relative to thatof the conventional grooved molding substrate.

[0078] In the eighth aspect of the prevent invention above, the slopingangle of the sidewall of the groove may be set to about 85° or more. Inthis case, since the sloping angle of the sidewall of the groove isabout 85° or more, noise is reduced, optical cross-talk between adjacenttracks is lowered, and thermal cross-talk (cross erasure) is reduced.Moreover, the wobble signal is accurately reproduced, CNR improves, anddropout of the various read-write signals becomes extremely low.

[0079] In the eighth aspect, the ratio of the groove depth d to thegroove width Gw may be set to about 0.1 or more. In such a case, thegreater the S/N ratio becomes, the lower the optical cross-talk betweenadjacent tracks and the thermal cross-talk (cross-erase) become.Moreover, the wobble signal is accurately reproduced, CNR improves, anddropout of the various read-write signals becomes extremely low.

[0080] In the eighth aspect, the groove may be a pit or discontinuity.In such a case, the arrangement of pits, or discontinuous grooves canrepresent binary information.

[0081] In a ninth aspect, the present invention provides memory mediawhose substrates are manufactured by any one of the methods formanufacturing a grooved molding substrate of the present inventiondescribed above.

[0082] In the ninth aspect, the memory medium means a medium on whichinformation can be recorded, such as optical disks, magneto-opticaldisks, hard disks, and the likes. Using these grooved molding substratesas a substrate of the memory medium, a hard disk having a high recordingdensity and a high S/N ratio can be obtained. In these memory media, theland is generally used for recording and the groove is generally usedfor tracking. Thus, the groove may be narrow although the land needs tohave a certain width. In the molding substrate according to the ninthaspect of the present invention, while the land width is limited by theminimum width determined by the exposure optical system, the groovewidth can be made narrower than this limit so that recording density canbe made high.

[0083] In a tenth aspect, the present invention provides memory deviceshaving the memory media according to the ninth aspect of the presentinvention above. In the tenth aspect, using these memory media, memorydevices having a high recording density and a high S/N ratio can beobtained.

[0084] In an eleventh aspect, the prevent invention provides computershaving the memory devices according to the tenth aspect of the presentinvention above. Using these memory devices as a memory device for thecomputer, a memory device having the same memory capacity can be madesmall, or a memory device having the same dimension can be made to havea more memory capacity.

[0085] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0086] In the following descriptions of the preferred embodiments, thephotoresist is classified into positive type (preferable) and negativetype. Master substrates are classified into master substrate I andmaster substrate II. As to grooves, grooves may be pits, hollows,discontinuous dints or the like.

[0087] According to the present invention, a molding substrate havingthe lowest groove width Gw of about 0.02 μm, or about 0.01 μm dependingupon circumstances, can be manufactured. One special feature of thepresent invention is to make it possible to manufacture a groove havinga width smaller than about 0.23 μm, which has not been achieved in theconventional art. In consideration of ease in manufacture and thisfeature of the present invention, the groove width is preferably about0.01 μm to about 0.23 μm, more preferably about 0.02 μm to about 0.1 μm,and further preferably about 0.03 μm to about 0.08 μm.

[0088] According to the present invention, it is possible to manufacturethe groove depth of about 1 nm to about 1 μm.

[0089] 1. Manufacturing Grooved Molding Substrate by Positive TypePhotoresist (FIGS. 1A-4C)

[0090] Master Substrate I

[0091] First, a substrate 3 is prepared. Although the substrate 3 isusually disk-shaped, it is possible for the substrate 3 to be polygonalor the like, not limited to a disk shape. Examples of the substrate 3material include glass materials. Suitable glass materials include sodalime glass (green plate glass), aluminosilicate glass (white plateglass), alkali-free glass, low-expansion glass, crystalline glass, andceramic materials. Quartz, for example, fused quartz or syntheticquartz, or even Si can be used as the ceramic material. Also, ifdesired, the substrate 3 may include a metal substrate material, suchas, Al, Fe, Cu, etc.

[0092] To prepare a master substrate, the substrate 3 surface ispolished with high precision in order to obtain a highly precisionsurface. It is also permissible to form a surface layer on the substratesurface. Examples of the suitable surface layer materials include:

[0093] (a) Silicon oxide compounds, such as SiO₂;

[0094] (b) Silicon-nitrogen compounds, such as Si₃N₄;

[0095] (c) Metal silicide compounds, such as TiSi₂;

[0096] (d) Metal, such as Ti, Al, Cu, Cr, Ta, Au, Ag, Pt, etc., and;

[0097] (e) Metal oxides or metal nitrides, such as TiO₂, TiN, Al₂O₃,AlN, TaO₂, Ta₂O₅, Ta₃N₄, etc.

[0098] Furthermore, it is also possible to form a surface layer byoxidation or nitration of the substrate surface. In many cases, thesurface layer is formed by thin layer deposition technology, forexample, vacuum deposition or sputtering. It is also possible in suchcases to form layers of two or more such materials. It is also possibleto utilize precision polishing, such as chemical mechanical polishing,etc., to improve the smoothness and flatness of the surface layer.

[0099] Having polished the substrate 3 surface, the surface is coatedwith a positive type D photoresist 2. The photoresist may be applied byspin coating. Usually, a primer, such as a silane coupling agentcoating, is applied to the substrate prior to photoresist coating. Thisprimer improves adhesion of the photoresist 2 to the substrate 3. Yet,there are instances where a primer is not needed, such as where Cr, TiN,etc., exist in the surface layer. In general, in master substrate I, thephotoresist depth determines the depth of pits and grooves. In the caseof the master substrate II (described below), the etching timedetermines the depth of grooves.

[0100] After having applied a photoresist 2 coating, a low temperaturepre-bake may be carried out to adjust the resist sensitivity.Subsequently, a laser beam recorder is used to illuminate the resistaccording to a prescribed pattern of pits, grooves, etc. The resist 2 isexposed in this manner.

[0101] A further explanation will be given in the case where a pluralityof grooves are formed in the pattern of concentric circular rings.First, the photoresist 2 is illuminated by the predetermined exposurelight with the effective spot diameter φ along a first line (O₁) via alens 1 (FIG. 1A). During the exposure, the substrate 3 together with thephotoresist 2 may be rotated relative to the first line O₁ around apredetermined center axis normal to the substrate surface to form agenerally annular-shape illumination area. (Of course, either theexposure light or the substrate may actually be rotated while the otheris fixed, or both may be rotated, to create the relative rotation.) Theilluminated area (exposed area) will correspond to a first land (groovein the conventional art) of the molding substrate that will bemanufactured. In FIG. 1A, φ denotes the aforementioned effective spotdiameter and, in this case, becomes equal to the land width Lw.

[0102] Then, the illumination position is moved from the first line O₁to a second line O₂ that is separated by a distance corresponding to thesum of the groove width Gw and the land width Lw of the grooved moldingsubstrate to be manufactured (FIG. 1B). Then, the photoresist 2 isexposed by exposing light. During the exposure, the substrate 3 togetherwith photoresist 2 may be rotated relative to the first line O₁ aroundthe predetermined center axis normal to the surface of the substrate sothat the corresponding annular portion of the photoresist 2 is exposed.This completes the exposure to the portion corresponding to the secondland. Here, if a parallel stripe-shape pattern is needed instead of theabove annular pattern, the substrate 3 can be translated relative to thefirst and second lines in a direction parallel to the surface of thesubstrate 3 during the exposure. Thus, the direction of the relativemovement between the optical axes and the substrate may be adjusted inaccordance with the target pattern to be formed on the photoresist 2.

[0103] Generally, the steps of moving the illumination position andilluminating (exposing) the photoresist 2 just described above arerepeated a plurality of times, successively regarding the second line inthe previous step as the first line in the repetition. This way, thephotoresist 2 is exposed along a plurality of concentric circular rings.The state where the exposure has completed is shown in FIG. 1C. Theexposed areas are denoted by “2 e.”

[0104] While the repetition of the steps of moving illumination positionand exposing the photoresist 2 is performed to form lands and grooves ina pattern of concentric circular rings, when a spiral shape is to beformed, the illumination (exposure) may be performed along a fictitiousspiral line on the photoresist instead of the repetition of these steps.

[0105] In the next step, the thus exposed resist 2 is immersed in adeveloping solution, and the resist is developed. Examples of thedeveloping solution include solutions of inorganic alkaline compounds,such as sodium phosphate, calcium phosphate, sodium hydroxide, calciumhydroxide, etc. It is also possible to use an organic, rather thaninorganic, alkaline solution. Since a positive type photoresist 2 isused here, the exposed area 2 e dissolves in the developing solution.The dissolved resist is washed with ultra-pure water and the underlyingsubstrate 3 is exposed at the dissolved portions. The substrate 3processed in this manner has a photoresist 2 pattern on its surface.This is shown in FIG. 2A. This type of photoresist pattern 2 togetherwith the substrate 3, or the pattern alone, is referred to as “resistpattern.” Such a resist pattern is referred to as the master substrate I(reference numeral 4).

[0106] After development, it is possible to heat the master substrate I(4) to a somewhat high temperature in a post-bake. A post-bake issometimes used to increase the sidewall angles of grooves and pits.Post-baking can also be used to improve the resistance of the resist toetching, to improve adhesion between the resist 2 and the substrate 3and also to harden the resist surface. By increasing the photoresisthardness, the patterned photoresist 2 is able to endure subsequentprocesses, including metallization and the formation of a plating layeron the conductive layer by an electroforming method.

[0107] Master Substrate II

[0108] First, the master substrate I (4) is prepared in a mannerdescribed above. In the master substrate I (4), since the exposedportions of the resist 2 are dissolved and the substrate 3 is exposed atthese exposed portions of the resist, the exposed regions of thesubstrate 3 can be etched so as to provide a concave region within thesubstrate 3. The thus created concave pattern corresponds to the resist2 pattern. The depth of the concave region is controlled by the etchingtime. The dry process is preferred for this etching although it ispossible to utilize a wet process. Among dry processes, the reactive ionetching (RIE) method is particularly advantageous. Other etchingprocesses that can be used include etching utilizing magnetron RIE,electron cyclotron resonance (ECR), induction-coupled plasma (ICP),helicon waves, etc. It is possible to use the RIE method using a normallow plasma density process (less than 10 ¹⁰ ions/cm³). However, a highplasma density process (greater than 10 ¹¹ ions/cm³) is preferred inorder to reduce the roughness of the etching region surface and thesidewall surface. Examples of such a high plasma density process includethe RIE utilizing ICP or helicon waves that are advantageous for formingparticularly fine patterns.

[0109] When dry etching is used, it is possible to form sharp sidewallangles within a front edge and a rear edge of a pit, with a preferredsidewall angle of about 90°. This is carried out to reduce reproductionsignal jitter of the optical disk, for example. When a ceramic mold(master substrate II) is used, the pit and groove sidewall are not asrough as those of the resist pattern (master substrate I). If dryetching is used, the bottom surface of the concavity and the surface ofthe sidewalls have an extremely low surface roughness after etching.Various etching methods, not limited to dry processes, can form ratherdeep concavities with sharp sidewall angles. A deep concavity and asteep concavity sidewall angle can impart various types of benefits toan optical disk. These benefits include reduction of noise, lowering ofoptical crosstalk between adjacent tracks, and reduction of thermalcrosstalk (cross erasure).

[0110] When a substrate 3 that has a surface layer is used, it ispossible to just etch the surface layer. If the surface layer materialand the underlying substrate material are etched at different rates,etching a substrate 3 that has a surface layer is advantageous since itbecomes possible to carry out etching uniformly. When such a substratewith a surface layer is etched, the thickness of the surface layerdetermines the depth of the grooves, etc.

[0111] Typically, in the manufacture of the master substrate II, theremaining resist is removed after the etching process. The removal maybe carried out by a dry etching process (ashing) using an oxygen plasma.Alternatively, the remnant resist is removed by immersion in a heatedcontainer holding a concentrated acidic solution, such as concentratedsulfic acid or concentrated nitric acid. Addition of hydrogen peroxideto such a solution improves resist removal. After the resist is removedin this manner, the substrate surface is washed with ultra-pure water,for example.

[0112] In this manner, a substrate that has protuberances correspondingto the pits and grooves shown in FIG. 8A is obtained. The resultantsubstrate is the master substrate II (reference numeral 4B) according tothe present invention. Ceramic material is particularly preferred as amaterial for constructing this substrate. Ceramic material is preferredsince the ceramic surface is very smooth. In other words, the roughness(Ra) of the ceramic material surface is extremely low (Ra=10 nm or Ra=1nm depending on circumstances). Optical disk noises are reduced whensuch a ceramic material is used for the manufacture of optical disks.The superiority of ceramic material sometimes is acknowledged byreferring to the master substrate II (4B) as “ceramic mold.”

[0113] Replica

[0114] A replica is modeled on the master substrate and hasconcavities-protuberances reversed from that of the master substrate.The material of the replica may be metal or resin. A metallic replica ismanufactured by electroformation on the master substrate. This method issimilar to the method for manufacturing a stamper, which will bedescribed below. However, a resin is preferable for the material of areplica. In particular, a resin is preferable when the master substrateI is used because a resin replica makes it possible to use the mastersubstrate I repeatedly. Thus, the case of using a resin replica isexplained below in detail.

[0115] First, a master substrate 4 (master substrate I or II) isprovided. A soft resin 7 is pressed against the concavity-protuberancesurface (signal surface) of the master substrate 4. Then, the resin 7 ishardened or cured as shown in FIG. 2B. The hardened or cured resin 7 isa copy of the concavities-protuberances of the master substrate. Theresin 7 is then peeled off from the master substrate to form a replica.

[0116] It is preferred that the resin 7 provides superior duplicationperformance when pressed against the master substrate. Resins with lowviscosity or high fluidity generally have good duplication performance.A typical method for lowering viscosity involves heating and softeningthe resin. In this case, the resin 7 is subsequently cooled andhardened. Alternatively, the resin 7 may be mixed with a solvent. Inthis case, the resin 7 hardens when the solvent is volatilized. Apreferred method employs a low viscosity material, such as a lowmolecular weight resin, prepolymer, or resin raw material. Additionally,such a material can be liquid. When the master substrate I is used forthe resist pattern, it is particularly preferable to use a liquid typeresin. It is also possible to mix a solvent with these materials tofurther lower the viscosity. In this case, a solid high molecular weightresin is used for polymerization (curing) of these materials at themaster substrate surface. The thus produced resin reproduces theconcavities-protuberances of the master substrate.

[0117] Among these methods, use of a low viscosity material, such as alow molecular weight resin, prepolymer, or resin raw material isparticularly preferable. A way to promote polymerization in this methodis heating or radiation exposure. Alternatively, two resin liquids maybe mixed together, and the resin mixture may be allowed to simply reactand polymerize. Ion beam radiation, electron beam radiation, ultravioletradiation, far ultraviolet radiation, laser light, x-rays, synchrotronradiation, etc., are examples of the types of radiation that may beused. Ultraviolet radiation, however, is preferred due to ease inhandling.

[0118] An example of the preferred method is explained with reference toFIGS. 2B and 2C. The master substrate 4 is placed with theconcavity-protuberance surface facing upward while a low-viscosityultraviolet-curing resin liquid 7 is poured slowly from above. Atransparent plate 8, such as a glass plate, may be placed upon the resinliquid so as to avoid the introduction of bubbles. Ultraviolet radiationmay be applied through the transparent plate 8, thereby causing theresin to cure. The cured resin 7 together with the transparent plate 8is peeled off from the master substrate 4. A replica 7 constructed oftwo layers—cured resin 7 and transparent plate 8—is obtained in thismanner.

[0119] A suitable transparent plate 8 may be a glass plate of at leastabout 0.6 mm thickness, preferably about 4 mm to about 10 mm thick. Theglass plate should have a surface roughness that is low in comparison tothat of the substrate 3 of the master substrate. A good surfaceroughness (Ra) value for the glass plate is about 5 nm to about 1 μm. Itis also possible to use resin materials, such as, polycarbonate,polystyrene, polyolefins, acrylic resins, etc., rather than glass plate.

[0120] When a glass plate 8 is used, after first cleaning the plate, aprimer, such as a silane coupling agent, may be used in order to improveadhesion between the resin and the glass plate. It is preferred that theprimer is heated (baked) after it is applied.

[0121] Examples of the silane coupling agents which may be used as theprimer include vinyl silanes, acrylsilanes, epoxy silanes, aminosilanes,etc. Examples of vinyl silanes include vinyltrichlorosilane,vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane,vinyltrimethoxysilane, etc.

[0122] Examples of acrylsilanes includeγ-methacryloxypropyltrimethoxysilane, etc. Examples of epoxy silanesinclude β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, etc. Examples of aminosilanesinclude N-β-(aminoethyl)-γ- aminopropyltrimethoxysilane,N-β-(aminoethyl)- γ-aminopropylmethyldimethoxysilane,γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane,etc. Other examples of silane coupling agents includeγ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, etc.

[0123] Examples of other primers include silanes, such as chlorosilanesand alkoxysilanes, silazanes, or special silylating agents. It is alsopossible to mix two or more of these primers. The primer can be used asa dilute solution in a solvent, such as toluene, xylene, ethanol,methanol, isopropanol, etc.

[0124] Examples of the resin of the replica are listed below. Generally,the resin can be classified as either (A) thermoplastic resins or (B)thermosetting resins.

[0125] (A) Thermoplastic Resins

[0126] Examples of thermoplastic resins include, but are not limited to,polycarbonates, polystyrenes, styrene-type polymer alloys, polyolefins,polypropylenes, amorphous polyolefins, acrylate resins (such aspolymethacrylates), polyvinylchlorides, thermoplastic polyurethanes,polyesters, nylons, etc.

[0127] (B) Thermosetting Resins

[0128] Examples of thermosetting resins include, but are not limited to,thermosetting polyurethanes, epoxy resins, unsaturated acrylate resins,etc. A preferred example is a curing resin solution mainly composed ofurethanated poly(meth)acrylate, polycarbonate di(meth)acrylate, andacetalglycoldiacrylate.

[0129] When a thermosetting resin is used, a low molecular weight resinliquid is made to contact the master substrate. This resin solution cancontain a curing catalyst or a curing agent. The curing catalyst is aphotosensitizer when curing takes place due to ultraviolet radiationexposure. Typical example of photosensitizers that may be used includeacetophenones, benzoin alkyl ethers, propiophenones, ketones,anthraquinones, thioxanthones, etc. It is also possible to use varioustypes of photosinsitizers mixed together. In particular,1-hydroxycyclohexyl phenyl ketone, etc., ketone-type photosensitizersare preferred due to their good duplication performance, moldreleasability, and stability. Resins that cure upon exposure toultraviolet light are called “ultraviolet curable resin,” and arepreferable for use as the resin of the stamper. Indeed, it is preferredthat the resin does not adhere to the stamper, particularly duringpeeling off from the resin replica in a later process.

[0130] As to the resin solution, in consideration of absorptioncharacteristics of heat and light, releasability of mold,light-resistance, durability, and hardness, it is preferable that thecolor number (APHA) is 30-50, and refractive index at 25° C. is 1.4-1.8.It is preferable for duplicating performance that the specific gravityand viscosity of resin solution at 25° C. are 0.8-1.3 and 10-4800 CPS,respectively.

[0131] In order to counter static electricity during the lastelectroforming process or ion plating process, it is possible to mix ananti-static agent into the resin liquid. Alternatively, a thinanti-static layer (such as a Pt layer) may be formed after the replicais completed. This type of anti-static treatment prevents problems, suchas burning, deformation, peeling, contaminant attachment, etc. The skinof the peeled resin replica from the master substrate 4 has generallysmall surface roughness Ra.

[0132] Stamper

[0133] A stamper 5 is manufactured by plating the replica 7 using eithera thick or a thin layer method (FIG. 3). The plating layer becomes thestamper 5. There are dry and wet plating methods. Among wet platingmethods, there exist non-electrolytic plating and electrolytic plating.The dry method is called “vacuum layer deposition.” Technologies forvacuum layer deposition include vacuum metallization, ion plating,sputtering, etc. Primary methods include dry plating andnon-electrolytic plating. An alternative method (secondary method) iselectrolytic plating. Plating may be carried out by either one of themethods.

[0134] The secondary method (electrolytic plating) is also called“electroforming.” Electrolytic plating can form a thick plating layer ina short time period. Prior to carrying out electroforming, since thereplica is not electrically conductive, a thin, generally about 30-100nm, metal layer is formed on the replica. This metal layer is called“conductive layer” and this process is called “metallization.”

[0135] Metallization is generally carried out by one of the primarymethods. Although Ni (nickel) is a preferred metal, other suitablemetals that may be used include Au, Pt, Pd, Ag, Ti, Ta, Cr, etc. It isalso possible to use other highly conductive metals or metal compounds.It is also possible to use a metal that contains phosphorous. Inparticular, when Ni is used as the metal, it is possible to first form aprimer layer made of another metal, or a metal containing compound, thathas a thermal expansion coefficient substantially equal to that of Ni.In such a case, the conductive layer is formed on this primer. During orafter electroforming, this primer layer can decrease the strainresulting from electroforming layer stress. This strain phenomenon maysometimes destroy the pits and grooves, and other concavities. Thisprimer layer may be removed after the stamper 5 is completed.

[0136] Then the resin replica with the conductive layer is immersed in aplating solution in order to carry out electroforming. Preferably, anickel sulfamate solution is used as this plating solution. A Ni platinglayer is formed on the conductive layer as electroforming is carriedout. This Ni plating layer is the stamper 5. It is also possible to usemetals other than Ni. Alternatively, it is possible to mix other metals,i.e., Ti or elements, e.g., P with the Ni. Mixture with P can result ina mold with a great surface hardness. It is possible to obtain a hardstamper with a long working life by the use of a Ni—P, Ti—P, or Ni—Ti—P,etc., and/or by the use of alloy composition for the conductive layer orplating layer, or both the conductive layer and plating layer.

[0137] Moreover, it is possible to add other plating layers, forexample, metals, such as silver, copper, or chrome, or alloys of suchmaterials, to the Ni plating layer instead of a simple Ni plating layer.

[0138] The stamper 5 can also be manufactured by dry plating ornon-electrolytic plating without using electroforming. The dry methodavoids the problem of waste water treatment. Among such dry methods, ionplating is capable of providing a stamper that has particularly a lowsurface roughness.

[0139] Concavities-protuberances of the stamper disappear as thedeposited plating layer thickness exceeds about 100 μm. That is to say,the surface of the plating layer appears flat. Generally, plating isstopped when the plating layer thickness reaches about 200 to about 600μm, preferably, about 250 μm to about 300 μm. The stamper 5 is thencompleted.

[0140] At the completion of formation of the stamper 5, the stamper 5 isstill attached to the replica 7. The stamper is thus peeled off from thereplica 7. This peeling must be carried out carefully since the stamper5 is a thin metal membrane (generally 250-300 μm thick). The peeledstamper 5 has a clean concavity-protuberance surface (shown in FIG. 4A).Although, in principle, it need not be cleaned, the stamper 5 may beoptionally cleaned. The washing treatment typically involves either wetwashing using organic solvent or purified water, or dry washing, such asashing, plasma treatment, ultraviolet exposure, ozone cleaning, etc.(See also FIGS. 4-5 of Hunyar, U.S. Pat. No. 4,211,617 and theaccompanying descriptions for a process for manufacturing a stamper froma replica.)

[0141] In order to improve the flatness of the stamper 5, prior topeeling off the stamper 5, or after peeling off the stamper, the backsurface of the stamper may be mechanically polished. When such polishingis carried out after peeling, the concavity-protuberance surface(information surface) of the stamper 5 is given a protective coating inorder to protect the stamper's concavity-protuberance surface. Thisprotective coating is formed by applying a peelable protective coating,followed by drying.

[0142] After the stamper 5 is peeled off from the replica 7 and its backsurface is polished, a hole is mechanically drilled in the vicinity ofthe center. The outer perimeter of the stamper 5 is removed in a similarmanner. This results in a finished annulus-shaped stamper. Shipment ofthe stamper is then possible.

[0143] The surface roughness Ra of the resultant stamper is generallysmaller than 10 nm. In most cases, a stamper has a surface roughnesssmaller than 1 nm. When a master substrate II is produced using the RIEmethod, the resultant stamper has almost no surface roughness. Thus itis possible to manufacture a particularly high quality stamper.

[0144] Forming Grooved Molding Substrate

[0145] A grooved molding substrate is manufactured using a method forforming a copy of the concavities-protuberances surface of the stamper(FIG. 4B). Thus, a grooved molding substrate 6 having a groove width Gwsmaller than the effective spot diameter φ is obtained. The formedgrooved molding substrate 6 is shown in FIG. 4C. As compared with thegrooved molding substrate manufactured in the conventional art, thegroove width according to the present invention can be made muchnarrower. Methods for manufacturing grooved molding substrate includeinjection, pressing, casting, etc. The injection molding method has thehighest productivity among these molding methods.

[0146] The resin that can be used for the grooved molding substrate ofthe present invention is generally a thermoplastic resin, particularly arelatively hard resin. Examples of such resins include polycarbonates,polystyrenes, styrene-type polymer alloys, acrylate resins (such aspolymethacrylates), polyvinylchlorides, polyesters, nylons,ethylene-vinylacetate resins, amorphous polyolefins, etc. However, it isalso possible to use a thermosetting resin if desired. Examples of suchthermosetting resins include epoxy resins, thermosetting polyurethanes,unsaturated acrylate resins, unsaturated polyesters,diethyleneglycol-bis-allylcarbonate resins, etc. Glass materials havinga low melting point can also be used instead of resins. The moldingtechnology for the grooved molding substrate that is similar to theconventional art may be used.

[0147] 2. Manufacturing Grooved Molding Substrate by Negative TypePhotoresist (FIGS. 5A-7)

[0148] Master Substrate I

[0149] First, a substrate 3 coated with a negative type photoresist 2 isprepared. Since the following explanation is similar to the above casewhere the positive type photoresist is used, brief explanations aregiven.

[0150] First, the photoresist 2 is illuminated by the exposure lightalong a first line O₁ (FIG. 5A). During the exposure, the substrate 3together with the photoresist 2 may be rotated relative to the firstline O₁ around a predetermined center axis normal to the surface of thesubstrate 3 to form an annular pattern of the illuminated (exposed)area. As a result, the portion corresponding to a first land is formed(the land width Lw=the effective spot diameter φ). Then, theillumination position is moved from the first line O₁ to a second lineO₂ that is separated by a distance corresponding to the sum of thegroove width Gw and the land width Lw (FIG. 5B). The photoresist 2 isthen illuminated by the exposure light. During the exposure, thesubstrate 3 together with the photoresist 2 may be rotated relative tothe second line O₂ around the center axis to form a circular pattern ofthe exposed area. This way, the exposure to a portion corresponding to asecond land (Lw=φ) is completed. Here, if a parallel stripe-shapepattern is needed instead of the above circular pattern, the substrate 3can be translated relative to the first and second lines in a directionparallel to the surface of the substrate 3 during the exposure. Thus,the direction of the relative movement between the optical axes and thesubstrate may be modified in accordance with the pattern to be formed onthe photoresist 2.

[0151] Generally, these movement and exposure steps described just aboveare repeated a plurality of times, regarding the second line in theprevious step as the first line in the current step. As a result, thephotoresist 2 is exposed along a plurality of concentric circular rings,for example. The state in which the exposure has completed is shown inFIG. 5C. The exposed areas are denoted by “2 e.” The unexposed areaswill become grooves.

[0152] Although the repetition of these steps is used for forming landsand grooves in the pattern of concentric circular rings, when a spiralshape is needed instead, illumination may be performed in a spiral shapein place of the repetition of these steps.

[0153] Then, the exposed resist 2 is developed. Since a negative typephotoresist 2 is used, the exposed areas 2 e remain, and the unexposedareas dissolve in the developing solution. As a result, a photoresistpattern 2 shown in FIG. 6A is obtained and, a master substrate I(reference numeral 4) constructed of the pattern 2 and the substrate 3is obtained.

[0154] Master Substrate II

[0155] First, the master substrate I (4) shown in FIG. 6A is prepared.Then, the master substrate II (reference numeral 4B) shown in FIG. 8B ismanufactured by etching and then removing residual resist in a mannerdescribed above in the context of manufacturing the master substrate IIusing a positive type photoresist.

[0156] Stamper

[0157] As shown in FIG. 6B, a stamper 5 is manufactured by plating themaster substrate 4 (while the master substrate II can also be used, themaster substrate I is used in the figure). The plating layer becomes thestamper 5. Further explanation is omitted because the method is the sameas that in the case of using a positive type photoresist describedabove. A free stamper 5 shown in FIG. 6C is obtained by peeling thestamper 5 from the master substrate 4.

[0158] Accordingly, when the negative type photoresist is used, there isan advantage that the stamper can be obtained directly from the mastersubstrate without using a replica.

[0159] Molding Substrate

[0160] A grooved molding substrate 6 having grooves 6 a and lands 6 b isformed of a resin or glass material by injection molding (resin) orpressing molding (glass) using the aforementioned stamper 5. See FIGS.6D and 7. Further explanation of the method is omitted because it is thesame as that in the case of using a positive type photoresist describedabove.

[0161] Hard Disk

[0162]FIG. 12 is a schematic cross-sectional view of a hard diskaccording to the present invention. A magnetic layer 22 is formed on asubstrate 21 having lands and grooves. The molding substrate accordingto the present invention can be used as the substrate 21 of the harddisk. The material for the substrate is preferably a resin or a glass,and particularly, a low-melting glass is preferable. The substrate 21has a spiral shaped groove or fine grooves in the pattern of concentriccircular rings. The magnetic layer 22 is made from CoCr, CoCrPt, CoCrTa,and/or the like deposited by sputtering. Depending on circumstances, aprotective layer and an under layer may be additionally formed on andunder the magnetic layer, respectively.

[0163] In this example of hard disk, information is recorded on thelands, and grooves are used for tracking. Accordingly, the lands have tohave a certain amount of width. The width has to be about the same orwider than that determined by the exposure optical system. On the otherhand, grooves can be made narrower according to the present invention.Therefore, the recording density can be increased by using the substrateof the present invention as the substrate 21.

[0164] Hard Disk Drive

[0165] As generally shown in FIG. 13, a hard disk drive according to thepresent invention is constructed of a data input terminal 31, and a dataprocessing circuit 34 for processing data passing through the terminal31, and a data recording/reproducing circuit 35 for converting the dataprocessed in the circuit 34 into recording data, transmitting to a head40, and for converting the data read by the head into reproductionsignals. The hard disk drive is configured to receive a hard disk 36 onwhich data is to be recorded through the head or reproduced through thehead 40. The hard disk drive further includes a motor 39 for driving thehard disk, a servo system control circuit 38 for controlling the motor39, a control data input/output terminal 32, a control data processingcircuit 37 for processing data input and output from the terminal 32,and a central processing circuit CPU 33 for controlling the circuits 34,37, and 38, and for performing various calculations. Of course, thepre-existing data recorded on the hard disk 36 is reproduced through thehead 40 and transmitted to the data recording/reproducing circuit 35.

[0166] The hard disk that is one of the recording media of the presentinvention can be used for the hard disk drive. In this case, a hard diskdrive having a high recording density can be obtained.

[0167] Computer

[0168] As generally shown in FIG. 14, a computer according to thepresent invention is composed of a central processing circuit CPU 41, amain memory 42 (semiconductor memories, such as DRAM, SRAM, and pseudoSRAM, for example) for connecting the CPU 41 to an address space, a harddisk drive 43 as a secondary memory device, a data input unit 44 (suchas keyboard, light pen, touch pad, digitizer, pen tablet, etc.), and adisplay 45 (such as CRT, liquid crystal display, etc.). The computeraccording to the present invention uses the hard disk drive of thepresent invention above.

FIRST WORKING EXAMPLE

[0169] A first working example is explained with reference to FIGS.1A-4C. The groove width Gw of the grooved molding substrate is 0.04 μmthat is smaller than the minimum groove width (0.23 μm) formed by theexposure light. The land width Lw of the grooved molding substrate ismade to be 0.36 μm.

[0170] (1) Master Substrate II

[0171] First, a synthetic quartz plate was prepared as a substratematerial. The substrate surface underwent precision polishing so as tohave a surface roughness Ra of less than 1 nm. After washing, a firstprimer (hexamethyldisilane) and then a photoresist were applied by spincosting on the substrate surface. The substrate then underwent pre-bake,resulting in a roughly 0.2 μm-thick photoresist layer 2 on the substrate3.

[0172] Then, a laser cutting machine was prepared. The laser lightsource was Ar laser. For the exposure light, the output light having awavelength of λ=351 nm was used. In this case, the effective spotdiameter φ was made to be 0.36 μm by adjusting the output of the lightsource and other elements. In the present invention, φ determines theland width Lw of the grooved molding substrate.

[0173] The resist 2 was exposed by the exposure light in a spiral-shapeland pattern. The exposure was carried out along the spiral such thatthe distance between the adjacent lines becomes the sum (0.40 μm) of thetarget groove width Gw (=0.04 μm) and the target land width Lw (=0.36μm) of the grooved molding substrate to be manufactured. In across-sectional view of the exposed photoresist 2 that includes theradial direction, the exposed areas 2 e and the unexposed areas werelocated alternately as shown in FIG. 1C. The exposed areas 2 ecorrespond to lands of the molding substrate to be manufactured, and theline width of the exposed area 2 e corresponds to the land width Lw ofthe grooved molding substrate that is to be manufactured. The line widthof each exposed area 2 e was 0.36 μm as a result of using the spotφ(=0.36 μm), which would produce lands having the land width of Lw=0.36μm. Accordingly, the width of each unexposed area became equal to thegroove width Gw=0.04 μm.

[0174] After the completion of exposure of the resist 2 on thesubstrate, the photoresist 2 was developed using an inorganic alkalinedeveloping solution. The resist surface was spin-cleaned, followed by apost-bake, resulting in formation of resist pattern 2 shown in FIG. 2A.The master substrate I (reference numeral 4) was thus manufactured.

[0175] Subsequently, the master substrate I (4) was loaded into areactive ion etching (RIE) apparatus, and dry etching was carried out.The etching was terminated when the depth reached to 80 nm.

[0176] The remaining resist was removed, and the substrate was cleaned,resulting in the master substrate II denoted by 4B in FIG. 8A. Thus, thepattern was created directly in the quartz substrate of the mastersubstrate II.

[0177] Since the master substrate II was manufactured using the RIEprocess, the groove sidewalls, the pit sidewalls, and the pit front andrear edges were all extremely sharp. Among others, this imparts thefollowing advantages (a)-(c) to the resulting optical disk:

[0178] (a) The wobble signal is accurately reproduced;

[0179] (b) CNR improves;

[0180] (c) Cross-erasure and crosstalk are reduced, dropout of thevarious read-write signals is extremely low, and noise also is greatlyreduced since the roughness of the pit bottoms, pit sidewalls, groovebottoms, and groove sidewalls is extremely low.

[0181] (2) Resin Replica

[0182] An ultraviolet-curing resin solution was provided. This resinsolution was prepared by mixing together (a) 70 parts of acetal glycoldiacrylate having the following structural formula (1),

[0183] where R₁ is independently H or CH₃, and R₂ is independently CH₃or C₂H₅; (b) 30 parts of urethane acrylate, which is a mixture ofcompounds having the following structural formula (2) and structuralformula (3),

[0184] R₅ is —CH₂CH₂CH₂CH₂O—[CH₂CH₂CH₂CH₂O]₂₀—CH₂CH₂CH₂CH₂—; and (c) 3parts of 1-hydroxycyclohexyl phenyl ketone (commercial productname=IRUGACURE 184, manufactured by Ciba-Geigy Corp.).

[0185] A green glass disk was prepared separately. This green glass diskhad a 200 mm outer diameter, a 10 mm inner diameter, and a 6 mmthickness. The disk was washed, and the surface was coated with silanecoupling agent (primer) by the spin shower method. A 120° C. bake wascarried out after the coating.

[0186] The master substrate 4 was placed with the concavity-protuberancesurface upward, and the resin solution 7 made as described above wasslowly poured on the substrate 4, as shown in FIG. 2B. The resinsolution 7 was poured carefully to avoid bubble entrapment. Then, theglass disk 8 was pressed against the master substrate 4 so that theviscous resin solution 7 can be spread uniformly across the entiresurface of the master substrate. 4.

[0187] Then, the resin solution 7 was exposed through the glass disk 8to ultraviolet radiation from a mercury lamp for about 5-60 seconds. Theresin solution 7 was cured by this way, resulting in a cured resin layer7. The hardened resin layer 7 becomes the replica. The structure of thereplica is shown in FIG. 2B.

[0188] Next, the replica 7 was peeled off from the master substrate 4.This was carried out with considerable care so as to avoid damaging thereplica and the master substrate. The surface roughness Ra of thereplica was less than 1 nm.

[0189] (3) Manufacturing a Stamper

[0190] The replica 7 was placed within a sputter apparatus, and a Nilayer (conductive layer) of a roughly 40-70 nm thickness was depositedon the surface to perform a conductive treatment. When theconcavities-protuberances of the replica are deep, sputtering ispreferably carried out in an RF discharge. An RF discharge is affectedadversely (for example, causing sputtering rate inhomogeneity) by staticelectricity on a replica. The sputtering was carried out in an RFdischarge (electric power=400 W).

[0191] When the Ni layer is thick, the Ni plating layer sometimessubsequently peels off. In such an instance, the thickness of the Nilayer (conductive layer) is then reduced by 10-40 nm.

[0192] After the conductive treatment, the replica was next placed in aplating solution into which nickel sulfamate had been dissolved. Thesolution temperature was about 45-55° C. Then, the power was turned onto start Ni electroforming. The current density was low at thebeginning. The current density was then gradually increased. Theelectroforming was terminated when the thickness of the resultant Niplating layer reached 293 μm. The resultant stamper 5 was made mainly ofthis plating layer. This is shown in FIG. 3.

[0193] As shown in FIG. 3, the stamper 5 was still attached to thereplica 7 immediately after production of the stamper 5. After thestamper 5 was peeled off from the replica 7, a free stamper 5 wasobtained, as shown in FIG. 4A. The stamper has a surface profile that isreversed from the concavities-protuberances of the molding substratethat is to be manufactured as the final product. The line widthcorresponding to the land width Lw of the grooved molding substrate was0.36 μm and the line width corresponding to the groove width Gw was 0.04μm. The surface roughness Ra of the stamper was less than 1 nm.

[0194] Spin coating was used to apply a protective coating (commercialproduct name: “CLEAN COAT-S,” manufactured by Fine Chemical Japan Inc.)on the stamper's concavity-protuberance surface. After coating, thecoating was allowed to dry naturally FOR 10 hours, thereby shielding theconcavity-protuberance surface with a protective coating. Afterpolishing the back surface of the stamper 5, a circular center hole wasbored, and unnecessary outer perimeter portions were removed, therebycompleting the manufacture of an annulus-shaped stamper 5.

[0195] The replica 7 was not damaged after the stamper 5 was peeledaway. Accordingly, the replica could be reused.

[0196] (4) Manufacturing a Grooved Molding Substrate

[0197] A Sumitomo Heavy Industries, Ltd., Model SD40 injection moldingmachine was used for injection molding. Polycarbonate (manufactured byTeijin Co., Ltd., product name: AD5503) was used as the resin of themolding substrate. This resin was loaded for feeding to this injectionmolding machine.

[0198] The stamper manufactured above was set in the molding machine.Molding of the molding substrate 6 was carried out under the followingconditions: 130° C. metal mold temperature, 340° C. resin temperature,30-metric ton injection pressure, and 12-second cycle time. Thesubstrate thickness was 0.6 mm. 600 grooved molding substrates 6 weremolded (manufactured) within 2 hours.

[0199] The shape and dimension of the grooves of the thus manufacturedgrooved molding substrate was observed and measured using an electronmicroscope (HR-SEM) and an atomic force microscope (AFM). The result ofthese observations showed that the groove depth, the land width, and thegroove width were about 80 nm, 0.36 μm, and 0.04 μm, respectively. Theslope of sidewall of grooves was steeper than 85°. A molding substratehaving such superior characteristics has never been reported before.

SECOND WORKING EXAMPLE

[0200] Another stamper was manufactured using the same method as in thefirst working example above. By using the stamper, a molding substratewith a plurality of grooves having a striped shape pattern (groove widthGw: 0.06 μm, land width Lw: 0.29 μm) was manufactured.

[0201] The shape and dimension of the grooves of the thus manufacturedgrooved molding substrate were observed using an electron microscope(HR-SEM) and an atomic force microscope (AFM). The result of theseobservations showed that the manufactured values are sufficiently closeto the target values.

[0202] According to the present invention, the grooved molding substratehaving the groove width less than the effective spot size φ (forexample, less than about 0.23 μm), which has not been achieved in theconventional art, can be manufactured in large quantities with low costby using injection molding or the like. A molding substrate havingsidewalls of groove steeper than 85° can also be manufactured in largequantities with low cost by using injection molding or the like. Themolding substrate according to the present invention is particularlyuseful for application to a hard disk.

[0203] It will be apparent to those skilled in the art that variousmodifications and variations can be made in the molding substrate, themanufacturing method thereof, and other aspects of the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents. In particular, although thepresent invention was explained in detail in the case of using themolding substrate as an optical disk, the molding substrate of thepresent invention, manufacturing method thereof, and other aspects ofthe present invention have various other applications. Any kind ofgrooved molding substrate having minute concavities-protuberances can bemolded in accordance with the present invention. Such a moldingsubstrate may have various applications, such as magnetic disks (harddisks), optical cards, liquid crystal display devices, semiconductordevices, printer components, data write-rewrite devices, personalcomputer components, automotive components, etc. Such a moldingsubstrate may also be optical components (such as zone plates, asphericlenses, diffraction gratings, holograms, photomasks, or reticles) orencoder components. Preferably, the molding substrate is a data storagedisk or an optical disk.

What is claimed is:
 1. A method for manufacturing a master substrate forproducing a grooved molding substrate, comprising: a preparing step thatprepares a substrate on which a photoresist is coated; an exposing stepthat exposes the photoresist to light with a predetermined pattern suchthat the exposed part corresponds to a land of the grooved moldingsubstrate to be produced; and a developing step that obtains the mastersubstrate by developing the photoresist.
 2. A method for manufacturing amaster substrate for producing a grooved molding substrate, comprising:a preparing step that prepares a substrate on which a photoresist iscoated; an exposing step that exposes the photoresist to light with apredetermined pattern such that the exposed part corresponds to a landof the grooved molding substrate to be produced; a developing step thatforms a resist pattern by developing the photoresist, the resist patternexposing a part of the substrate; an etching step that etches the partof the substrate exposed in the developing step; and a removing stepthat obtains the master substrate by removing the photoresist.
 3. Amethod for manufacturing a master substrate for use in producing agrooved molding substrate, comprising: a first step that prepares asubstrate on which a photoresist is coated; a second step that exposesthe photoresist with exposing light, the resultant photoresist having aportion that is exposed to the exposing light and a portion that is notexposed to the exposing light, the exposed portion corresponding to aland of the grooved molding substrate to be produced, the unexposedportion corresponding to a groove of the grooved molding substrate to beproduced; and a third step that obtains the master substrate bydeveloping the photoresist exposed in the second step.
 4. The methodaccording to claim 3 , wherein the second step includes the steps of:forming a part corresponding to a first land of the grooved moldingsubstrate to be produced, by illuminating and exposing the photoresistalong a first line with the exposing light; moving an illuminatingposition from the first line to a second line that is separated from thefirst line by a distance corresponding to the sum of a groove width Gwand a land width Lw of the grooved molding substrate to be produced; andforming a part corresponding to a second land of the grooved moldingsubstrate to be produced, by illuminating and exposing the photoresistalong the second line with the exposing light.
 5. The method accordingto claim 4 , wherein the groove width Gw is about 0.1 μm or less.
 6. Themethod according to claim 4 , wherein the groove width Gw is about 0.06μm or less.
 7. The method according to claim 4 , wherein the groove ofthe grooved molding substrate is at least one of a pit, a hollow, anddiscontinuity.
 8. The method according to claim 4 , wherein the step ofmoving an illuminating position from the first line to a second line andthe step of forming a part corresponding to a second land of the groovedmolding substrate to be produced are repeated in that order a pluralityof times by successively regarding the second line in the previousexecution of the two steps as the first line in the repetition.
 9. Themethod according to claim 3 , wherein the second step includes a stepthat forms a part corresponding to a spiral-shaped land of the groovedmolding substrate to be produced, by illuminating and exposing thephotoresist along a spiral line, the spiral line having an intervalcorresponding to the sum of a groove width Gw and a land width Lw of thegrooved molding substrate to be produced.
 10. The method according toclaim 9 , wherein the groove width Gw is about 0.1 μm or less.
 11. Themethod according to claim 9 , wherein the groove width Gw is about 0.06μm or less.
 12. The method according to claim 9 , wherein the groove ofthe grooved molding substrate is at least one of a pit, a hollow, anddiscontinuity.
 13. A method for manufacturing a master substrate for usein producing a grooved molding substrate, comprising: a first step thatprepares a substrate on which a photoresist is coated; a second stepthat exposes the photoresist with exposing light, the resultantphotoresist having a portion that is exposed to the exposing light and aportion that is not exposed to the exposing light, the exposed portioncorresponding to a land of the grooved molding substrate to be produced,the unexposed portion corresponding to a groove of the grooved moldingsubstrate to be produced; a third step that obtains a resist pattern bydeveloping the photoresist exposed in the second step; a fourth stepthat etches a part of the substrate in accordance with the resistpattern; and a fifth step that removes the photoresist from thesubstrate processed in the third step to obtain the master substrate foruse in producing the grooved molding substrate.
 14. The method accordingto claim 13 , wherein the second step includes the steps of: forming apart corresponding to a first land of the grooved molding substrate tobe produced, by illuminating and exposing the photoresist along a firstline with the exposing light; moving an illuminating position from thefirst line to a second line that is separated from the first line by adistance corresponding to the sum of a groove width Gw and a land widthLw of the grooved molding substrate to be produced; and forming a partcorresponding to a second land of the grooved molding substrate to beproduced, by illuminating and exposing the photoresist along the secondline with the exposing light.
 15. The method according to claim 14 ,wherein the groove width Gw is about 0.1 μm or less.
 16. The methodaccording to claim 14 , wherein the groove width Gw is about 0.06 μm orless.
 17. The method according to claim 14 , wherein the groove of thegrooved molding substrate is at least one of a pit, a hollow, anddiscontinuity.
 18. The method according to claim 14 , wherein the stepof moving an illuminating position from the first line to a second lineand the step of forming a part corresponding to a second land of thegrooved molding substrate to be produced are repeated in that order aplurality of times by successively regarding the second line in theprevious execution of the two steps as the first line in the repetition.19. The method according to claim 13 , wherein the second step includesa step that forms a part corresponding to a spiral-shaped land of thegrooved molding substrate to be produced, by illuminating and exposingthe photoresist along a spiral line, the spiral line having an intervalcorresponding to the sum of a groove width Gw and a land width Lw of thegrooved molding substrate to be produced.
 20. The method according toclaim 19 , wherein the groove width Gw is about 0.1 μm or less.
 21. Themethod according to claim 19 , wherein the groove width Gw is about 0.06μm or less.
 22. The method according to claim 19 , wherein the groove ofthe grooved molding substrate is at least one of a pit, a hollow, anddiscontinuity.
 23. A method for manufacturing a stamper for producing agrooved molding substrate, comprising the steps of: obtaining a mastersubstrate manufactured using the method according to any one of claims1-4, 9, 13-14, and 19 using a positive type photoresist as thephotoresist; forming a replica from the master substrate, the replicahaving a surface profile that is reverse of the surface profile of themaster substrate; and producing the stamper from the replica using anelectroforming method.
 24. The method for manufacturing a stamper forproducing a grooved molding substrate according to claim 23 , whereinthe replica is made of at least one of a metal and a resin.
 25. A methodfor manufacturing a stamper for producing a grooved molding substrate,comprising the steps of: obtaining a master substrate manufactured usingthe method according to any one of claims 1-4, 9, 13-14, and 19 using anegative type photoresist as the photoresist, and producing the stamperfrom the master substrate using an electroforming method.
 26. A methodfor manufacturing a stamper comprising steps of: a preparing step thatprepares a substrate on which a photoresist is coated; an exposing stepthat exposes the photoresist to light with a predetermined pattern; adeveloping step that forms a resist pattern by developing thephotoresist; an etching step that etches a part of the substrate notcovered by the photoresist; a removing step that obtains a mastersubstrate by removing the photoresist; a replica forming step that formsa resin replica from the master substrate; and a stamper producing stepthat produces the stamper from the replica using an electroformingmethod.
 27. A method for manufacturing a grooved molding substratecomprising the steps of: obtaining a stamper manufactured using themethod of claim 23 ; and producing the grooved molding substrate byforming one of a glass and a resin with the stamper.
 28. A method formanufacturing a grooved molding substrate comprising the steps of:obtaining a stamper manufactured using the method of claim 25 , andproducing the grooved molding substrate by forming one of a glass and aresin with the stamper.
 29. A grooved molding substrate manufactured byan injection molding method using a stamper, wherein the groove width Gwis about 0.1 μm or less.
 30. The grooved molding substrate according toclaim 29 , wherein the groove width Gw is about 0.06 μm or less.
 31. Thegrooved molding substrate according to claim 29 , wherein the slopeangle of the sidewall of the groove is about 85° or more.
 32. Thegrooved molding substrate according to claim 29 , wherein the ratio ofthe groove depth d to the groove width Gw is about 0.1 or more.
 33. Thegrooved molding substrate according to claim 29 , wherein the groove isat least one of a pit and a discontinuity.
 34. A memory medium asubstrate of which is manufactured by the method for manufacturing agrooved molding substrate according to claim 27 .
 35. A memory medium asubstrate of which is manufactured by the method for manufacturing agrooved molding substrate according to claim 28 .
 36. A memory medium asubstrate of which is the grooved molding substrate of claim 29 .
 37. Amemory device having the memory medium according to claim 34 .
 38. Amemory device having the memory medium according to claim 35 .
 39. Amemory device having the memory medium according to claim 36 .
 40. Acomputer having the memory device according to claim 37 .
 41. A computerhaving the memory device according to claim 38 .
 42. A computer havingthe memory device according to claim 39 .